In numerous manufacturing and material handling operations, it is necessary to transfer normally non-fluent materials, such as liquids, which are too viscous to flow at ambient conditions, comminuted solids, slurries of comminuted solids, normally solid materials, which are liquefied at elevated temperatures, etc. It is, of course, necessary to transport such materials to and from reaction vessels, storage vessels, and the like. So long as the material is continously moving and there are no restrictions of any type in the transport lines few problems arise since the lines can be heated as by steam tracing, electrical tape, etc. and/or pressure can be applied to maintain flow. However, serious problems do arise when it is necessary to interrupt flow for some reason. Such interruptions include plant turnarounds, emergency shutdowns, sampling and a large number of other such interruptions. In certain of these instances, such as sampling, it is impractical or uneconomical to maintain the system in a heated and/or pressurized condition at all times, while in most other instances of shutdown the heating and/or pressurizing system is also shutdown. As a result the material being transported will solidify, form plugs or become unduly viscous during a shutdown. Obviously, in most cases, the interruption of flow requires a valve of some type. This, of course, adds to the problem, to the extent that valves are more difficult to maintain in a heated condition and the valve in and of itself is a flow restriction even under normal operating conditions. In addition, once a system is shut down, the valve becomes plugged. Heating and/or pressurizing is only a partial solution since such heating and/or pressurizing causes undue delays in start-up and in some instances damages equipment, such as pumps which are usually started before the material is sufficiently fluent to be pumped. One of the major operations in which these problems are encountered is in the handling and transport of normally solid plastics or resins. These materials are obviously best transported in a liquid condition but once the heating system is shut down for some reason or only intermittent transport is necessary, the material will obviously solidify and plug any flow lines and valves. In addition, in many operations, in the handling of normally solid plastics or resins, the valves are lubricated with the plastic or resin itself in order to prevent contamination. Other operations include sulfur units in which sulfur freezes on valves when they become cold, or where valves are utilized in a normally heated condition and must necessarily be lubricated with highly viscous lubricants which will have a tendency to plug conventional valves when cooled.
While numerous valves have been developed in the art, and many for the handling of normally non-fluent materials, such valves have one major drawback, namely the flow path through the valve is restricted, thus adding to the problems encountered in the handling of normally non-fluent materials or materials which have a tendency to plug readily. This is true since the closure means of such valves are located within the valve body and thus flow is annularly, about, under or through the closure means itself. The tendency to plug, therefore, is great. Plug type valves are one solution to this problem. However, elaborate and expensive sealing, lubrication, etc. are necessary in most of these valves.